Commercial Street preserves the course of a wagon trail that predated the town and formed one path of the Mountain Route of the Santa Fe Trail. From 1821 until 1878, thousands of ox-drawn freight wagons passed here carrying trade goods in both directions between towns near Kansas City, Missouri, and Santa Fe, New Mexico. The Santa Fe Trail was primarily a route of commerce rather than immigration. Because the trail was here before the town began developing in the 1860s, Commercial Street curves in two blocks and shows unusual widening and jutting opposite this point. Historians theorize the trail curved and descended narrow Mill Street to the original bridge over the river, several hundred yards downstream of today's Commercial Street bridge. In the trail's first decades, most wagon trains used the Cimarron Route across northeast New Mexico to avoid difficult Raton Pass, which often required a week or more to cross. After improvements to the pass road in the 1860s, the Mountain Route, with more reliable water sources and fewer Indian attacks and thefts, carried a major share of the trail's traffic. Wagon trains continued through Trinidad until the railroad arrived in 1878 and ended the need for the trail.